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Perhaps not the number one cause of issues on the Forum, but certainly in the top 5, is assuming a new part is "good" when you install it.
I'd pick up a cheap IR temp gun from Harbor Freight or Amazon, and confirm that the thermostat is operating as it should. You have a very shiny engine compartment, so shoot it at the upper radiator hose, as the IR temp gun will be confused by all of the reflections.
I'd also confirm the timing, and not trust a dyno sheet.
From: At my Bar drinking and wrenching in Lafayette Colorado
If you have a 2" filter element in a drop base air cleaner housing there is no way that you have adequate clearance between the carb airhorn and the bottom of the air cleaner lid. I have made multiple posts about this. Here are the facts:
.
A few years ago, I did a bit of dyno testing on air cleaners. What we found to have the greatest effect on engine power and performance is the distance from the top of the carb's airhorn to the bottom of the air cleaner lid. Once this distance gets tight, as it does when people use the drop-base air cleaners with a low-profile air filter to gain hood clearance, power is dramatically affected, and the car will "nose over" at elevated rpm or power setting, much like vapor lock. I found that the minimum distance from the carb's air cleaner gasket on the airhorn to the bottom of the air cleaner lid, to avoid serious upper-rpm performance problems, is 3 inches. Most air cleaners have a 1" "dome", which means that the minimum distance from the air cleaner gasket on the carb to the top surface of the air filter is 2 inches. Anything less than that and you will have issues. So, for instance, you cannot run a 2" tall air cleaner on a drop base - it puts you way below the 2" minimum height required above the carb. Check your heights and clearances. Run the tallest filter you can, and get the air cleaner lid as far above the airhorn as you can without hitting the hood.
To test this, just run the carb without the air cleaner lid installed and see if your problem persists or not. Obviously, if your hood is so tight to the carb that the 3" rule is still not met, you will have the problem even without the air cleaner lid installed, so you may have to "pop" your hood release and run the test with the hood raised and unlatched to verify.
Lars
From: At my Bar drinking and wrenching in Lafayette Colorado
No - that still interferes with the smooth flow of air into the airhorn/venturis. You need the 3-inch minimum dimension regardless of the type of air cleaner top you use.
[QUOTE=lars;[url=tel:1609529884]1609529884[/url]]If you have a 2" filter element in a drop base air cleaner housing there is no way that you have adequate clearance between the carb airhorn and the bottom of the air cleaner lid. I have made multiple posts about this. Here are the facts:
.
A few years ago, I did a bit of dyno testing on air cleaners. What we found to have the greatest effect on engine power and performance is the distance from the top of the carb's airhorn to the bottom of the air cleaner lid. Once this distance gets tight, as it does when people use the drop-base air cleaners with a low-profile air filter to gain hood clearance, power is dramatically affected, and the car will "nose over" at elevated rpm or power setting, much like vapor lock. I found that the minimum distance from the carb's air cleaner gasket on the airhorn to the bottom of the air cleaner lid, to avoid serious upper-rpm performance problems, is 3 inches. Most air cleaners have a 1" "dome", which means that the minimum distance from the air cleaner gasket on the carb to the top surface of the air filter is 2 inches. Anything less than that and you will have issues. So, for instance, you cannot run a 2" tall air cleaner on a drop base - it puts you way below the 2" minimum height required above the carb. Check your heights and clearances. Run the tallest filter you can, and get the air cleaner lid as far above the airhorn as you can without hitting the hood.
To test this, just run the carb without the air cleaner lid installed and see if your problem persists or not. Obviously, if your hood is so tight to the carb that the 3" rule is still not met, you will have the problem even without the air cleaner lid installed, so you may have to "pop" your hood release and run the test with the hood raised and unlatched to verify.
I will give that a try. I will see exactly how much clearance I actually have with the hood shut. Thanks
1609529884]If you have a 2" filter element in a drop base air cleaner housing there is no way that you have adequate clearance between the carb airhorn and the bottom of the air cleaner lid. I have made multiple posts about this. Here are the facts:
.
A few years ago, I did a bit of dyno testing on air cleaners. What we found to have the greatest effect on engine power and performance is the distance from the top of the carb's airhorn to the bottom of the air cleaner lid. Once this distance gets tight, as it does when people use the drop-base air cleaners with a low-profile air filter to gain hood clearance, power is dramatically affected, and the car will "nose over" at elevated rpm or power setting, much like vapor lock. I found that the minimum distance from the carb's air cleaner gasket on the airhorn to the bottom of the air cleaner lid, to avoid serious upper-rpm performance problems, is 3 inches. Most air cleaners have a 1" "dome", which means that the minimum distance from the air cleaner gasket on the carb to the top surface of the air filter is 2 inches. Anything less than that and you will have issues. So, for instance, you cannot run a 2" tall air cleaner on a drop base - it puts you way below the 2" minimum height required above the carb. Check your heights and clearances. Run the tallest filter you can, and get the air cleaner lid as far above the airhorn as you can without hitting the hood.
To test this, just run the carb without the air cleaner lid installed and see if your problem persists or not. Obviously, if your hood is so tight to the carb that the 3" rule is still not met, you will have the problem even without the air cleaner lid installed, so you may have to "pop" your hood release and run the test with the hood raised and unlatched to verify.
I will give that a try. I will see exactly how much clearance I actually have with the hood shut. Thanks
I checked today and you are correct. Way under 3” from the airhorn. I can get a standard 3” filter on without the lid but with the lid it hits. I might have to change the intake manifold to a lower profile. This is definitely an issue so thanks for your advice😁
From: At my Bar drinking and wrenching in Lafayette Colorado
Good job on the setup and check. That could very well be the source of your troubles, and if it's not the only source, it's contributing adversely to your performance - my numbers show that you could be down 15-20hp with the air cleaner lid sitting that close to the top of the carb airhorn. I'd be interested in the results of a test drive with the 3" filter installed on the air cleaner base, the air cleaner top left off, and the hood closed over the top of the 3" element... some aluminum foil rolled up and crumpled around the perimeter of the 3" filter to "squish" against the hood.
Lars
I had to purchase a flat Allstar Performance aluminum air cleaner lid to get 2” of clearance between the air horns and lid and still get clearance between the lid and hood with a 3” element.
I’m using a drop base air cleaner, but I’m running a Quick Fuel racing carb so the total design works.
Last edited by OldCarBum; Mar 26, 2026 at 12:49 AM.
If you run the test Lars recommended with no improvement, ignition coils and ignition modules can begin to fail when they warm up.
Even new doesn’t mean they aren’t failing.
Before you start tearing off and replacing the intake check all the little easy to swap things first.
You might even send Lars some pictures of your QJet and see what he thinks.
It may need some of his expertise.
Last edited by OldCarBum; Mar 26, 2026 at 12:56 AM.
It sounds like you may have a tank vent problem. The first thing I would try is either drilling a vent hole in the gas cap or driving it without the gas cap. a vented gas cap flows about the same amount of air into the tank as a 0.080 restriction, but you are pulling fuel out with a 3/8" fuel line. if the car has an evap canister it may be plugged with age thus not allowing enough air into the tank thus creating a vacuum in the tank causing the fuel pump to starve.
Tried running the car without the air cleaner and I got about a mile away and back to fuel starvation and off to the side of the road. Outside temp was about 75 degrees and the car had been idling outside my shop before I left for about 20 min with a temp around 180. When I broke down the car was about 175-180 with a quick check of the thermal gun that I brought. I sat with the hood open for over a half hour and still would not start. Had my wife bring me a little gas and primed the carb, It started and i got about 200 yards and it died. Repeated the prime and she fired up and I drove the rest of the way home without any issues. Absolutely crazy...
Tried running the car without the air cleaner and I got about a mile away and back to fuel starvation and off to the side of the road. Outside temp was about 75 degrees and the car had been idling outside my shop before I left for about 20 min with a temp around 180. When I broke down the car was about 175-180 with a quick check of the thermal gun that I brought. I sat with the hood open for over a half hour and still would not start. Had my wife bring me a little gas and primed the carb, It started and i got about 200 yards and it died. Repeated the prime and she fired up and I drove the rest of the way home without any issues. Absolutely crazy...
When it broke down did you try to check for spark? Pull the coil wire out of the distributor cap and lay it near anything metal, crank and see if you have a spark or take a timing light with you and when you have the issue hook up the light and see if it flashes.
Not sure whether you have HEI or points based system. Either way heat can cause coil breakdown.
1609538659[/url]]When it broke down did you try to check for spark? Pull the coil wire out of the distributor cap and lay it near anything metal, crank and see if you have a spark or take a timing light with you and when you have the issue hook up the light and see if it flashes.
Not sure whether you have HEI or points based system. Either way heat can cause coil breakdown.
Have electronic ign. I did check and it was getting good spark. I’m almost positive it’s an intermittent fuel issue.
Try swapping out the coil and the ignition module.
They are cheap.
If it’s idling fine when cold without issues then starts giving you problems when it warms up, it could be the coil of module going bad.
If you are using the oem resistor wire (usually pink) to power your electronic ignition, that could also be an issue.
If you really want to diagnose the problem rather than doing a parts swap you will need to start eliminating things. Like Lars told you about the air cleaner space. Next step would be checking the fuel system. Your description sounds like when you prime it, it starts. You should push down on the accelerator pump or pump the throttle while looking to see if it squirts fuel. No fuel means it’s on that side not the ignition side or visa versa. Next if it’s on the fuel side run a hose down to the intake side of the pump and put the other end in a small remote fuel tank (something that won’t leak all over). I have an old 3 gallon moon tank. Strap it on and run the car. This will tell you if the problem is on the tank side or fuel pump side. Then diagnose from there. Fuel pressure for the pump, possible fuel filter depending on where or if there is one, bad needle seat or possibly hot fuel line which can be temporarily insulated. You get the picture.
So Lars post really got me thinking about this. I am running a 4 inch tall filter with the L88 drop base. I am running the L88 air chamber as a cold air box. Popped my air cleaner lid off and sure enough I only have 2 inches of clearance with the 4 inch element. Seems as if even the stock L88 cars would have had an issue with this as well with their small 3 inch tall element.
Thanks everyone. I’ll figure this thing out but not at home for a couple of weeks. I appreciate all the advice and let you all know if it was something weird or just missed. Bill
